Data response Example 8

Data Response question on coal

 Teacher only box

I have made up this question to help prepare students for the data response questions which appear on Section A of Paper 3 for the examinations on the 2014 programme (i.e. for examinations after May 2016). The information given is new to the students but they should be able to use their knowledge and understanding of the chemistry content of the programme to answer the questions. Because I have tried to make the chemistry interesting it may be a little harder than an actual exam question but exposure to questions like this beforehand should make students able to face the data response question in the final examination with considerable confidence. All the answers require a knowledge and understanding of material from the core only so this particular question is suitable for both Standard and Higher Level students.

As well as including model answers I have also explained the chemistry fully and given the 'Complete course for students' links to the pages which cover the theory behind each individual question. If you set it as an assigned task using Student Access, students will not be able to see the model answers until after they have submitted their answers to you. If you simply give students access to the page (rather than assigning it as a task) they will be able to access the model answers themselves for review/revision/self-study etc.

If you do not wish to use student access, links to downloadable versions of the questions and, separately the worked answers, can be found at Printable versions of written tasks.

 

Coal is an abundant fossil fuel. The different grades of coal can be classified according to the percentage of carbon they contain.

(a) Analysis of a sample of coal shows that it contains 90.5% carbon, 4.2% hydrogen and 0.8% sulfur by mass.
Identify the name of the grade of coal this sample belongs to. [1]

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(b) (i) Assuming no other elements in the sample of coal combust, use Section 13 of the data booklet to determine the theoretical heat content of 1.00 kg of this particular sample of coal. [2]

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(ii) Suggest one reason why the value obtained for (b) (i) is higher than the value given in the table above for this particular grade of coal. [1]

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(c) The combustion of coal is one of the main causes of carbon dioxide pollution in the atmosphere. In 2011 it is estimated that the total amount of coal combusted worldwide was 7.695 x 109 tonnes, which added 1.442 x 1010 tonnes of carbon dioxide into the atmosphere.
Assuming that coal contains on average 87% by mass of carbon and that all the carbon burned to form carbon dioxide, calculate the percentage of coal that did not release carbon dioxide into the atmosphere when it was combusted in 2011. [2]

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(d) ”Carbon capture” describes different methods in which carbon dioxide produced by coal combustion is prevented from entering the atmosphere. One such method is called “mineral sequestration” and involves reacting the carbon dioxide with naturally occurring metal silicates such as forsterite, Mg2SiO4.

The equation for the reaction is:

Mg2SiO4(s) + 2CO2(g) → 2MgCO3(s) + SiO2(s)

Explain why carbon dioxide is a gas at STP whereas silicon dioxide is a solid with a high melting point (1600 oC). [2]

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(e) The products of coal combustion can also cause acid deposition.

(i) State one equation to show how the products from the combustion of coal can lead to acid rain. [1]

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(ii) Outline why rainwater needs to have a pH below 5.6 before it is classified as “acid rain”. [1]

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